High power dissipation matrix for a character display tube

ABSTRACT

A matrix configuration having a plurality of slits surrounding a group of character apertures is disclosed. Each slit is located along a line formed by a moving point having both a radial and a circumferential component. Typical slits have an approximately spiral appearance. Such slits have the characteristics of providing sufficient flexibility to accommodate differential thermal expansion in the matrix sheet without warping or distortion while permitting rapid dissipation of the heat from the matrix to the supporting structure.

United States Patent inventor Johannes Mueller Su D l CHI.

Appl. No. 838,621

Filed July 2, I969 Patented July [3, I971 Aulgnee Stronrlnrg Dlaraphlx, Inc. San Diego, Calll.

HIGH POWER DISSIPATION MATRIX FOR A CHARACTER DISPLAY TUBE 3 Chhn, 6 Drawing Figs.

[1.8. CI 313/86, 313/39 Int. Cl ..H0lj 29/46, H01j6l/$2,H0lj 31/16 Fleltl of Search 313/86, 350, 76, 77, 78, 89,269, 348, 92

xx xxxxxxxxxx xxxxxxxxxx XXXX XXXXX XXXXXXXX Xxxxxxxxxx XXXXXXXXXX XXXXXXXXXX XX XX XXXX [56] References Cited UNITED STATES PATENTS 3.178.603 4/1965 Moss 313/86 3,305,748 2/1967 Pehe et al. 3 l 3/350 X 3.500,l00 3/l970 Murdock 313/86 Primary Examiner- Robert Segal Attorney-John R. Duncan ABSTRACT: A matrix configuration having a plurality of slits surrounding a group of character apertures is disclosed. Each slit is located along a line formed by a moving point having both a radial and a circumferential component. Typical slits have an approximately spiral appearance. Such slits have the characteristics of providing sufficient flexibility to accommodate differential thermal expansion in the matrix sheet without warping or distortion while permitting rapid dissipation of the heat from the matrix to the supporting structure.

PATENTED JUL! 3197:

SHEET 1 BF 3 mvewmn. JOHANNES MUELLER Mam ATTORNEY PATENTEUJULIBIS?! 3,593 053 SHEET 2 0F 3 owe/v. J ES MUE R JPAQM ATTORNEY PATENTEU JUL 1 3 IBTI SHEET 3 OF 3 VIII/l/I/l/I/I/III/A uvvtwron. JOHANNES MUELLER ATTORNEY BACKGROUND OF THE INVENTION Cathode-ray tubes utilizing character shaped apertures in a matrix sheet to shape an electron beam such as originally described by Joseph T. McNaney, et al., in [1.8. Pat. No.

2,824,250, are now well known. in such a tube, thin electron l opaque sheet bearing a plurality of character-shaped apertures is located across the electron beam path within the tube. After the electron beam passes through the matrix it will have a cross-sectional shape conforming to the desired character shape. The shaped beam is then directed to the tube face, where it typically impinges on a phosphor coated screen whereby an area is energized or illuminated corresponding to the selected character aperture through which the beam passed. In this manner a great many characters may be rapidly formed on the tube face to provide a visible display for direct viewing or for copying with any suitable photosensitive system. Character display tubes have proved to be highly effective in producing displays at high character printing rates with excellent character quality and resolution. Such tubes have come into wide commercial use.

Problems, however, remain in maintaining the required high character resolution and sharpness over the life ofa tube due to the warping and distortion of the thin matrix sheet which results from differential thermal expansion across the sheet during operation of the tube. The matrix sheets tend to be very thin, generally having thickness less than about 0.00I inch. In some tubes, the matrix is located only about 0.03 to about 0.06 inch from the cathode. Thus, even very slight warping, bulging or distortion of the matrix can adversely affect the quality of the characters generated on the tube face.

Only a relatively small proportion of the electron beam which reaches the matrix is passed on through the character apertures. The remainder of the beam is absorbed by the matrix sheet, resulting in severe heating. Also, when the matrix sheet is located very near the cathode, it will be heated by radiation from the cathode. This heating is, of course, the greatest near the center of the matrix. Thus, differential thermal expansion of the matrix will result in severe stresses which may produce warping and other distortions of the matrix. The entire center portion of the matrix may move toward or away from the cathode, resulting in distortion of the characters. in an extreme case, the heating of the matrix sheet may become so severe as to cause melting of the material. This is most severe with characters such as the letter which requires very narrow bridges between the center of the letter and the surrounding material. These bridges being very small are susceptible to melting which will result in the displacement of the center portion so that the letter 0" on the tube face will appear as a spot of light rather than a circumferential line.

Attempts have been made to minimize the distortion caused by the differential expansion across some characters matrix sheet. As described in copending Application Ser. No. 452,679, filed May 3, 1965, now US. Pat. No. 3,500,l00, wrinkling of the matrix sheet may be minimized by surrounding the character group with a series of small slits or accordion pleats. The small slits are arranged in one or more rows substantially parallel to the outer edge of the group of characters. The slits or pleats are intended to permit the matrix to expand or contract and distort only in these areas which are outside of the character bearing area of the matrix. While these slits tend to alleviate the distortion problem they have been found to ad versely increase the heat dissipation problem. These slits greatly decrease the path for heat flow outwardly from the character bearing area of the matrix to the surrounding supporting structure. Even the slight overheating of the matrix will then cause the small bridges in some characters to melt which severely distorts the letter shapes.

Thus, there is a continuing need for an improved character matrix configuration which both eliminates warping or other distortion in the matrix during use and permits rapid dissipation of heat from the character bearing area of the matrix outwardly to the matrix sheet supporting structure.

SUMMARY OF THE INVENTION It is, therefore, an object of this invention to provide a character matrix configuration which overcomes the abovenoted problems.

It is another object of this invention to provide a character matrix configuration which permits high heat dissipation rates.

it is still another object of this invention to provide a character matrix which is not subject to wrinkling, warping or distortion during operation in a character display tube.

The above objects, and others, are accomplished in accordance with this invention by providing at least one ringlike array of angular slits surrounding the active character area of a character matrix sheet. Each of the slits is formed by a point which simultaneously moves outwardly away from said active character area and circumferentially around said active character area. A typical slit which might be formed by this simultaneous radial and circumferential movement would be approximately spiral in appearance. It has been found that the circumferential component of this slit adds flexibility in the slit area to accommodate differential thermal expansion within the matrix without warping or other distortion while the radial component maintains a suitable heat path for heat dissipation from the character bearing area to the surrounding supporting structure.

A wide variety of suitable slit configurations may be developed within the overall requirement of both radial and circumferential components an especially preferred embodiment, the slits have a generally spiral appearance, with the strips between the slits having a uniform width. The distance between the slits maintained constant along a line normal to the centerline of the interslit strip. This maintains a constant width heat dissipation path while giving excellent flexibility for thermal expansion accommodation.

The slits may have any suitable width. Free space is required to accommodate thermal expansion. This space may be provided by relatively few wide slits or relatively many narrow slits, as desired. Excessively wide slits are undesirable, however, since they decrease the heat conducting cross sections of the interslit strips.

The slits may have any suitable length. It is highly desirable that the outer end of the slit at least overlap the inner end of the second adjacent slit to give the maximum flexibility. However, if the slits are excessively long, the heat path along the interslit strips may be undesirably long. On the other hand, if the slits are excessively short then the slit area will not have the desired flexibility to accommodate difl'erential thermal expansion.

The slits may have their inner and outer ends in any suitable location. For example, the inner and outer ends of the slits may be located along concentric circles surrounding the matrix character area. It is preferred that the inner ends of the slits start along a rectangular or other shape which closely sur rounds the matrix character area. This eliminates the relatively large solid areas adjacent to the character array which are more likely to warp or wrinkle. Alternatively, if desired, the inner and outer ends of the slits may be located in a staggered manner at different distances from the center of the character bearing matrix.

The matrix sheet may comprise any suitable material. in general, it is preferred that the matrix sheet be made up of a material having a high melting point such as tungsten, rhenium, and molybdenum. However, because of the excellent heat dissipation characteristics of the matrix configuration of this invention, some materials with otherwise undesirably low melting points may be suitable where they have other characteristics which are advantageous. Also, multilayer bimetalic sheets (such as nickel platedsilver or copper alloy sheets) may be used without excessive distortion due to differing thermal expansion characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS Details of the invention and of several preferred embodiments thereof will be further understood upon reference to the drawings wherein:

FIG. I shows a simple schematic representation of a character display tube utilizing a character bearing matrix according to this invention;

FIG. 2 shows an elevation view of an especially preferred matrix configuration according to this invention;

FIG. 3 shows an alternative embodiment of the character matrix using straight slits;

FIG. 4 shows another alternative embodiment of the character matrix using a double row of slits;

FIG. 5 shows another alternative embodiment of the character matrix using reverse curve slits; and

FIG. 6 shows a section through the matrix of FIG. 5 taken on line 645 in FIG. 5 together with the supporting means.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1 there is seen a cathode-ray tube of the character display type generally designated I0. Display tube I0 includes beam generating and projecting means 11. Deflection plates 12 and 13 are vertical and horizontal deflection plates, respectively, which effect positioning of beam 14 to direct the beam 14 through the desired one or more shaped apertures on matrix sheet IS. The magnetic deflection coils (not shown) will generally be located outside the tube at the junction between the neck and funnel of the envelope. The shaped electron beam 14 leaving matrix 15 is then redirected in known manner, such as by the magnetic deflection coils and positioning deflection plates 24 and 25 which deflect the beam for presentation at desired position on screen 21.

The cathode-ray tube shown in FIG. 1 is merely exempliary of those within which matrix sheets such as matrix 15 may be utilized. Other tubes utilizing matrix sheets include those described in U.S. Pat. Nos. 2,737,956 and 2,761,988, and others.

An especially preferred embodiment of the improved matrix sheet according to this invention is shown in FIG. 2.

As seen in FIG. 2, matrix sheet 15 has a central active character area which includes a plurality of character shaped apertures which may include alpha-numeric symbols or other symbols as desired. An array of x characters is shown for simplicity. The symbols may be laid out in any suitable array. A plurality of slits 31 surround the active character area 30. Each slit has both a radial and a circumferential component. In order to obtain a uniform heat conduction path along the strips between adjacent slits, the width of the strips is maintained constant; that is, the width of each slit along a line normal to the centerline will be substantially constant. The length of each slit is sufficient to provide flexibility within the slit area to accommodate thermal expansion within matrix sheet I5. As is strongly preferred, the outer end of each slit extends pasta line drawn outwardly from the center of the active character area through the inner end of the second adjacent slit. Typically, as seen in FIG. 2, the outer end of slit 34 extends past hypothetical line 35 drawn from the center of active character area 30 through the inner end of slit 36. Matrix sheet 15 is mounted within supporting ring structure 32 which is preferably made of a material having high thermal conductivity to act as a heat sinlt for matrix sheet 15.

While the configuration shown in FIG. 2 is preferred because of its optimum combination of heat dissipation characteristics and thermal expansion accommodating characteristics, other configurations may be used, if desired.

FIG. 3 shows an alternative embodiment of the slit system described above.

Here, the character apertures (not shown) lie within a boundary line which outlines the edges of active character area on matrix sheet 4|. In this embodiment, slits 42 are in the form of straight lines having both a radial and a circumferential component. Of course, these lines could have portions which are entirely circumferential or entirely radial, so

long as the overall slit has the required combination. Also, in this embodiment, the inner ends of the slits 42 are arranged on a circle, rather than closely adjacent the boundary of active character area 40. This embodiment is simple and economical to manufacture and has good heat dissipation and expansion characteristics.

If desired, multiple rows or rings of slits may be used, as illustrated in FIG. 4. Here matrix sheet 50 bearing an active character area generally shown at 51, includes an inner ring of slits $2 and an outer ring of slits 53. Where only a single ring of slits is used, thermal expansion of the matrix will cause very slight rotation of the active character area as the slits accommodate the expansion. Ordinarily, this very slight rotation is not objectionable. However, this rotation can be substantially eliminated by providing a second ring of slits which have a circumferential component moving in a direction opposite to that of the inner slits.

Where two generally concentric rings of slits are used, it is preferred that the ring between the slit rings be thicker than the remainder of the sheet. This thickening can be accomplished in any conventional manner, such as by electroplating or laminating additional metal in this area. The additional metal will aid in equalizing temperature around the matrix at this location, and will aid in eliminating the slight rotation of the active character area which results where a single array of slits is used. In the dual slit ring configuration, the inner ring of slits will cause slight rotation in one direction as the temperature of the active character area rises and heat is conducted away along the interslit strips. The thickened ring just beyond the outer ends of the first slit array will be sufficiently rigid to prevent distortion and will tend to equalize the temperature. Then, as the heat is conducted outwardly through the interslit strips in the outer slit array to the supporting structure, stresses developed due to differential thermal expansion in the rigid ring and the outer slit array will be accommodated by slight rotation of the rigid ring (and, of course, the portion of the matrix sheet within the ring) in a direction opposite to the rotation generated by the inner slit array. Thus, thermal expansion will cause very slight rotation in both directions, leaving the active character area substantially unaflected.

FIG. 5 shows an alternative embodiment in which the slits have a reverse curve; that is, the direction of the circumferential component of the slit changes. The matrix sheet, generally designated 50, includes an active character area SI. The slits include an inner portion 52 having a circumferential component in one direction and an outer portion 53 having a circumferential component in the opposite direction. This reverse curve arrangement will tend to eliminate rotation of the active character area 5] as the matrix 50 is heated, since the two slit portions 52 and 53 will tend to cause rotation in opposite directions. Also, thermal expansion may be partially accommodated by compression of the slit area and/or bending of the interslit strips.

While the arrangement shown in FIG. 5 has excellent heat dissipation and thermal expansion accommodating characteristics, the interslit strips tend to be so flexible as to possibly permit vibration add excessive movement out of the plane of matrix sheet 50. It is therefore preferred that a support structure such as that shown in section in FIG. 6 be used with the embodiment of FIG. 5. The support structure of FIG. 6 is also useful with other embodiments of the matrix of this invention.

As seen in FIG. 6, the support structure includes two ring shaped members. Lower support 56 has a generally planar upper surface, while upper support 55 has a recessed lower surface. Matrix sheet 50 is positioned between supports 55 and 56. In this figure the area of matrix 50 which contains the active character area and slit area is indicated by a broken line. The outer rim 59 of matrix 50 is tightly clamped between supports 55 and 56. The slit area on matrix 50 is located adjoint recess 58 in upper support 55. Thus, the slit area is free to expand in the plane of matrix 50, but is restrained from excessive movement out of that plane. Also, the portions of supports 55 and 56 which lie adjacent the slit area will help to remove heat from matrix sheet 50.

While the supports may extend over the slit area to any desired degree, it is preferred that they substantially cover the slit area. In addition to preventing excessive displacement of the matrix sheet, the support will tend to prevent portions of the electron beam from passing through the slits and reaching the tube face.

Although specific slit arrangements shapes and proportions have been described in the above descriptions of preferred embodiments, these may be varied within the scope of this disclosure with similar results. For example, slit spacing may be irregular, and slits having various shapes may be used, if desired.

Other modifications and ramifications of the invention will become apparent to those skilled in the art upon reading the present disclosure. These are intended to be included within the scope of this invention as defined in the claims.

lclaim:

1. The matrix system according to claim 5 wherein the outer ends of said first plurality of slits are arranged substantially along a circle; the inner ends of said second plurality of slits are arranged along a larger circle; and the ring-shaped portion between these circles is thicker than the remainder of the matrix sheet.

2. A matrix system for a character display tube comprising a sheet having a plurality of character apertures arranged in an active character area and a plurality of outwardly extending slits in said sheet arranged around said active character area; the line of each of said slits formed by a point moving radially away from said active character area and circumferentially around said active character area; the outer end of at least some slits extending circumferentially beyond a straight line drawn outwardly from the center of said active character area through the inner end of the second adjacent slit; and a second plurality of slits provided around the first plurality of slits, with the circumferential component of said second plurality of slits moving in the opposite direction from that of said first plurality of slits, whereby distortion within said active character area is reduced and heat is rapidly dissipated from said active character area when said matrix is used in a character display tube.

3. A matrix system for a character display tube comprising a sheet having a plurality of character apertures arranged in an active character area and a plurality of outwardly extending slits in said sheet arranged around said active character area; the line of each of said slits formed by a point moving radially away from said active character area and circumferentially around said active character area; the outer end of at least some slits extending circumferentially beyond a straight line drawn outwardly from the center of said active character area through the inner end of the second adjacent slit, and the circumferential component of at least a portion of said slits being in the direction opposite to the circumferential portion of the remainder of said slits, whereby distortion within said active character area is reduced and heat is rapidly dissipated from said active character area when said matrix is used in a character display tube. 

1. The matrix system according to claim 5 wherein the outer ends of said first plurality of slits are arranged substantially along a circle; the inner ends of said second plurality of slits are arranged along a larger circle; and the ring-shaped portion between these circles is thicker than the remainder of the matrix sheet.
 2. A matrix system for a character display tube comprising a sheet having a plurality of character apertures arranged in an active character area and a plurality of outwardly extending slits in said sheet arranged around said active character area; the line of each of said slits formed by a point moving radially away from said active character area and circumferentially around said active character area; the outer end of at least some slits extending circumferentially beyond a straight line drawn outwardly from the center of said active character area through the inner end of the second adjacent slit; and a second plurality of slits provided around the first plurality of slits, with the circumferential component of said second plurality of slits moving in the opposite direction from tHat of said first plurality of slits, whereby distortion within said active character area is reduced and heat is rapidly dissipated from said active character area when said matrix is used in a character display tube.
 3. A matrix system for a character display tube comprising a sheet having a plurality of character apertures arranged in an active character area and a plurality of outwardly extending slits in said sheet arranged around said active character area; the line of each of said slits formed by a point moving radially away from said active character area and circumferentially around said active character area; the outer end of at least some slits extending circumferentially beyond a straight line drawn outwardly from the center of said active character area through the inner end of the second adjacent slit, and the circumferential component of at least a portion of said slits being in the direction opposite to the circumferential portion of the remainder of said slits, whereby distortion within said active character area is reduced and heat is rapidly dissipated from said active character area when said matrix is used in a character display tube. 